Synthetic resin preform to be biaxially stretched and blow molded into a bottle

ABSTRACT

The blow molded preform of a laminated wall structure comprises a bulging shoulder portion, which has a diameter that widens slightly in the downward direction; a bottom shell portion for molding the bottom, which has been blow molded from the corresponding portion of parison P so as to have a widened and deformed shape; an inner overhang wall portion in any position starting from the opposite side of the neck ring and ending at the upper portion of the bulging shoulder portion, with the inner wall portion having a diameter that widens in the downward direction; and/or a radially widened connecting portion of an arced shape, which has a larger diameter than the barrel portion so that the entire bottom including the bottom shell portion takes a bulging spherical shape. With this configuration, no thick area is formed in the inner overhang wall portion on the opposite side of the neck ring and/or in the pinch-off portion.

CROSS-REFERENCE

This is a Division of application Ser. No. 10/129,081, filed on Jun. 12,2002, which is a U.S. National Stage of PCT/JP01/11159, filed Dec. 20,2001. The entire disclosure of each of the prior applications is herebyincorporated by reference herein in its entirety.

TECHNICAL FIELD

This invention relates to the structure of a preform that is biaxiallystretched and blow molded into a synthetic resin bottle, andparticularly to the type of preform that has been molded by a blowmolding means, among other types of preforms that have been molded intothe primary molded intermediates of a cylindrical shape having a closedend.

BACKGROUND ART

As the synthetic resin preforms that have been molded into the primarymolded intermediates and are to be biaxially stretched and blow moldedinto bottles, there are known those preforms of a cylindrical shapehaving a closed end, which have been molded by an injection moldingmeans or a blow molding means. As compared to the injection moldedpreforms, the blow molded preforms can be obtained at less expensivecosts, more freely molded into various shapes, and are easy to adopt thelaminated wall structures.

Thus, the blow molded preforms have the following advantages. Firstly,their cost of equipment is lower than the corresponding cost forinjection-molded preforms, and the blow-molded products can be sold at alower price than the injection molded ones. Secondly, because they arehighly versatile in selecting shapes, the preforms can be molded into ashape that fits in with the appearance of a bottle to be molded.Thirdly, because they are easy to adopt the laminated wall structures,the thin-wall bottles can be obtained while desired physical propertiescan be effectively maintained.

However, the above prior art has a problem in that local thick areastend to occur in the shoulder portion and on the underside of the bottomof the molded bottle. Because of these thick areas, the molded bottleshave a bias of thickness in the walls, thus resulting in decreasedprecision in the overall wall thickness.

SUMMARY

This invention has been made to solve such a problem observed in priorart. The technical problem of this invention is thus to prevent localthick areas from occurring in the preform. The object of this inventionis to obtain those bottles having high precision in the overall wallthickness and thus having no distortion in their appearance.

In this invention made to solve the above-described technical problem,the means of carrying out the invention may comprise:

-   -   employing a blow-molded preform so that the preform is molded        into a bottle by a biaxially stretching and blow molding means;    -   providing the preform with a mouth portion;    -   providing the preform with a cylindrical barrel portion from        which the barrel is molded;    -   providing the preform with a bulging shoulder portion from which        the shoulder is molded, disposing this portion between the mouth        portion and the barrel portion, and allowing the bulging        shoulder portion to have the diameter that widens slightly in        the downward direction;    -   providing the preform with a bottom shell portion for molding        the bottom, which portion has been blow molded from the        corresponding portion of parison P so as to have a widened and        deformed shape;    -   providing the preform with an inner overhang wall portion an        inner overhang wall portion (3′) in any position starting from        the opposite side of the neck ring (3), which is disposed        circumferentially around the lower part of the mouth portion        (2), and ending at the upper portion of the bulging shoulder        portion (4′), with the inner wall portion (3′) having a diameter        that widens in the downward direction; and    -   providing the preform with certain laminated wall structures.

The means of carrying out the invention may also comprise:

-   -   employing a blow-molded preform so that the preform is molded        into a bottle by a biaxially stretching and blow molding means;    -   providing the preform with a mouth portion;    -   providing the preform with a cylindrical barrel portion from        which the barrel is molded;    -   providing the preform with a bulging shoulder portion from which        the shoulder is molded, disposing this portion between the mouth        portion and the barrel portion, and allowing the bulging        shoulder portion to have the diameter that widens slightly in        the downward direction;    -   providing the preform with a bottom shell portion for molding        the bottom, which portion has been blow molded from the        corresponding portion of parison P so as to have a widened and        deformed shape;    -   providing the preform with a radially widened connecting portion        (6′) connecting the lower part of the cylindrical barrel portion        (5′) with the bottom shell portion (7′), with the connecting        portion (6′) having a larger diameter than the barrel portion        (5′); and    -   providing the preform with certain laminated wall structures.

DISCLOSURE OF THE INVENTION

In certain exemplary embodiments of the invention, for example, thebulging shoulder portion may have a diameter that widens slightly in thedownward direction. As a result, the barrel portion has a largerdiameter than the mouth portion. This makes it possible to lower thepercent of stretch in the circumferential direction when the preform isbiaxially stretched and blow molded into a bottle. According to thisinvention, even those bottles having a high blow ratio can be moldedwith high stability and good moldability. The shape of the bulgingshoulder portion can be selected from among those suitable for thepurpose. For example, a linear or curved slope can be used.

The bottom shell portion for molding the bottom has been blow moldedfrom the corresponding portion of parison P in the widened and deformedshape. With the preform of such a shape, the bottom of the bottle isstretched and blow molded in the circumferential direction. Thepinch-off portion of the bottom shell portion is also stretched, even ifthe pinch-off portion is generally thick because this portion of thepreform is derived from the pinch-off scar in the parison P. Thus, thethick area is prevented from occurring in the bottom.

Any widened and deformed shape of the bottom shell portion can beselected depending on purpose and necessity and in response to the shapeintended for the bottom of a bottle. For example, the preform can be inan isotropic shape. The preform bottom may have a shape similar to thebottom of the bottle but in a reduced proportion. In that case, thebottom of the bottle is stretched almost uniformly in thecircumferential direction. Even if any distorted deformation takes placeat the bottom, this deformation is circumferentially uniform. Therefore,there is no case where this deformation caused by distortion maydeteriorate the appearance and shape of the bottle or where the deformedbottom makes the bottle unstable.

In other exemplary embodiments of the invention, the neck ring isdisposed circumferentially around the mouth portion at its lower partwhere no stretching occurs. The inner overhang wall portion is disposedin any position starting from nearby the opposite side of the neck ring,which is disposed circumferentially around the lower part of the mouthportion, and ending at the upper portion of the bulging shoulderportion, with the inner wall portion having a diameter that widens inthe downward direction. Even if a local thick area is formed by pushingthe core guide into the parison mouth when the parison is blow molded,this thick area in the inner overhang wall portion does not remain thickbecause blow molding operation forces this area to be stretched anddeformed.

In certain exemplary embodiments of the invention, the means of carryingout the invention comprises that the bottom shell portion to be moldedinto the bottom of the bottle has a roughly spherical shape.

Because the bottom shell portion to be molded into the bottom of thebottle has a roughly spherical shape, the preform can be blow molded ina mold of a simple shape to achieve isotropically widened deformationand expanded deformation. Especially in the bottle having a bottom of aroughly isotropic cross section, the bottom of the preform is stretchedalmost uniformly in the circumferential direction. Even if any distorteddeformation takes place at the bottom, this deformation iscircumferentially uniform. Therefore, there is no case where thisdeformation caused by distortion may deteriorate the appearance andshape of the bottle or where the deformed bottom loses its stablesitting function.

In other exemplary embodiments of the invention, the preform comprises aradially widened connecting portion connecting the lower part of thecylindrical barrel portion with the bottom shell portion, and thisconnecting portion has a larger diameter than the barrel portion. Whenthe parison is blow molded into a preform, the bottom shell portion,along with this radially widened connecting portion, is stretched anddeformed up to the last moment of blow molding and in a locallyconcentrated manner.

Because of a pinch-off scar in the parison, the pinch-off portion of thebottom shell is generally thick, but it is largely stretched up to thelast moment of the blow molding and in a locally concentrated manner. Sothe pinch-off portion has a decreased wall thickness and does not remainthick.

In other exemplary embodiments of the invention, the means of carryingout the invention comprises that the bottom shell portion to be moldedinto the bottom of a bottle has a roughly spherical shape and that theradially widened connecting portion connects the lower part of thecylindrical barrel portion with the bottom shell portion, and has alarger diameter than the barrel portion so that this portion has abulging shape.

In the above-described configuration, the preform comprises the bottomshell portion of a roughly spherical shape and a radially widenedconnecting portion of an arced shape that connects the lower part of thecylindrical barrel portion with the bottom shell portion, and thisconnecting portion has a larger diameter than the barrel portion so thatthis portion makes an arc. With this configuration, the parison can beblow molded in a mold of a simple shape to achieve isotropically wideneddeformation and expanded deformation and thereby to form the bottomshell portion and the radially widened connecting portion. Especially inthe bottle having the bottom and the radially widened connecting portionof a roughly isotropic cross section, the bottom and the connectingportion of the preform are stretched almost uniformly in thecircumferential direction. Even if any distorted deformation takes placeat the bottom, this distorted deformation is circumferentially uniform.Therefore, there is no case where this distorted deformation maydeteriorate the bottle appearance and shape or where the deformed bottomloses its stable sitting function.

In still other exemplary embodiments of the invention, the inventionalso comprises an inner overhang wall portion in any position startingfrom the opposite side of the neck ring, which is disposedcircumferentially around the lower part of the mouth portion, and endingat the upper portion of the bulging shoulder portion, with the innerwall portion having a diameter that widens in the downward direction.

In this exemplary embodiment, thick areas are prevented from occurringin both of the pinch-off portion and the inner overhang portion in anyposition starting from the opposite side of the neck ring and ending atthe upper portion of the bulging shoulder portion.

In other exemplary embodiments of the invention, the means of carryingout the invention comprises at least one of the bulging shoulderportion, the cylindrical barrel portion, and the bottom shell portionhaving a shape similar to the shoulder, the barrel, or the bottom,respectively, of the bottle, but on a reduced scale.

For example, the preform is given partly or entirely a bottle-like shapeon a reduced scale. Such a shape gives the preform more uniform percentof stretch than usual, when the preform is biaxially stretched and blowmolded into a bottle. Even if the bottle has a complicated shape, suchas being largely non-isotropic, or having a shape with various ups anddowns, there can be obtained a less deformed bottle of uniform thicknesswith high stability and good moldability.

In certain other exemplary embodiments of the invention, the means ofcarrying out the invention comprises a reinforcing rib disposed on thedownside of the pinch-off portion in the bottom shell portion.

The pinch-off portion is welded by the crushing power of the blow moldwhen the parison is pinched off. Even if a groove-like sink mark isformed due to the welding failure in the surface of the pinch-offportion (the inner surface of the bottom shell portion), the reinforcingrib can make up for the decrease in the weld area caused by this sinkmark. When the preform is biaxially stretched and blow molded into abottle, the reinforced pinch-off portion can be blow molded withoutrupture, thus giving assurance for the stable biaxial-stretching andblow-molding operation.

In the perform of various exemplary embodiments of the invention, it hasbecome possible to combine laminates of synthetic resin materials havingdifferent physical properties and thereby to mold those bottles in whichdesired physical properties or functions are effectively utilized. Theresin combinations also make it possible to utilize safely even thosemolding materials, such as the regenerated resin materials, which mayarouse concern for their use unless they are subjected to furthertreatment.

In another exemplary embodiment of the invention, the means of carryingout the invention comprises the laminated wall structure consisting ofat least a layer of polyethylene terephthalate resin (hereinafterreferred to as PET) and a layer of polyethylene naphthalate resin(hereinafter referred to as PEN).

PET is mainly used as the PET resins in this invention. However,polyester copolymers containing ethylene terephthalate units as themajor component and other polyester units can also be used, unless thesubstance of PET is lost. Other components for obtaining polyestercopolymers include the dicarboxylic acid components, such as isophthalicacid, naphthalene-2,6-dicarboxylic acid, and adipic acid; and the glycolcomponents, such as propylene glycol, 1,4-butanediol, tetramethyleneglycol, neopentyl glycol, cyclohexane dimethanol, and diethylene glycol.

Amorphous PET resins can also be used as PET. These amorphous PET resinsshow no melting peak when they are measured for the melting temperature,Tm, on the differential scanning calorimeter (DSC). As an example, PETG(Eastman Chemical) is available, which is obtained by copolymerizing PETwith such a glycol component as cyclohexane dimethanol.

The PEN resins used in this invention are the polyester copolymerscontaining PEN comprising ethylene-2,6-naphthalate units and otherethylene-2,6-naphthalate units at a concentration of 50 mol % or more.As the examples of acid components of the copolymer, there may bementioned terephthalic acid, isophthalic acid, andhexahydro-terephthalic acid. The glycol components of the copolymerinclude, for example, 1,3-propanediol, tetramethylene glycol,1,4-cyclohexane dimethanol, and neopentyl glycol.

The PET resin layer is combined with the PEN resin layer. Thiscombination serves to enhance effectively the properties that seem to bedeficient in the PET resin, such as thermal resistance, resistance tochemicals, and UV-cutting property.

In yet other exemplary embodiments of the invention, the means ofcarrying out the invention comprises the laminated wall structureconsisting of at least the outer and inner layers of a PET resin and themiddle layer of a gas barrier resin. The gas barrier resins, which arewell known in the art and can be used in this invention, include nylonresins, such as nylon-6, nylon-66, and polyamide containing xylyleneradicals; the ethylene vinyl alcohol polymer; and the polyacrylonitrileresin.

In this exemplary embodiment of the invention, there is obtained abottle having enhanced barrier properties against oxygen and carbondioxide, as these barrier properties are deficient when a single PETlayer is used.

In other exemplary embodiments of the invention, the means of carryingout the invention comprises the laminated wall structure consisting ofat least the outer layer of polyethylene or polypropylene and the innerlayer of an ethylene vinyl alcohol copolymer or the PET resin. Like thePET resins used in earlier described exemplary embodiments of theinvention, the PET resins used include amorphous PET resins.

This laminated wall structure prevents the adsorption of limonene,vitamins, etc., among other effective components of the bottle contents.

In other exemplary embodiments of the invention, the means of carryingout the invention comprises the laminated wall structure consisting ofat least the outer layer of polyethylene or polypropylene, the middlelayer utilizing a gas barrier resin, and the inner layer of polyethyleneor polypropylene.

In this exemplary embodiment of the invention, it is possible to obtainbottles having a high oxygen barrier property.

In other exemplary embodiments of the invention, the means of carryingout the invention comprises the laminated wall structure consisting ofat least the outer layer of a nylon resin and the inner layer ofpolypropylene or polyethylene. The nylon resins usable in this inventioninclude nylon-6, nylon-66, and polyamide containing xylylene radicals.

In this exemplary embodiment of the invention, it is possible to obtainbottles having a high piercing strength and high surface gloss becauseof the nylon resin used as the outer layer.

Other exemplary embodiments of the invention also comprise the laminatedstructure consisting of at least the inner and outer layers of a virginresin material and the middle layer of a regenerated resin material,which makes it possible to utilize regenerated resin materials safely.

In other exemplary embodiments of the invention, the means of carryingout the invention comprises that an antistatic additive is added to theouter layer of the laminated wall structure.

An antistatic agent may be added to the outer layer alone. Thus, with asmall amount of additive, it is possible to prevent the bottle frombeing electro-statically charged over the outer surface whereelectrostatic charge is a problem.

In other exemplary embodiments of the invention, the means of carryingout the invention comprises that a UV-absorbing agent is added to atleast one of the layers of the laminated wall structure.

The UV-absorbing agent can be added to the most effective layer inresponse to the layer configuration and the application of the bottle.

In other exemplary embodiments of the invention, the means of carryingout the invention comprises the laminated wall structure consisting ofat least the outer layer of a synthetic resin and the inner layer ofanother synthetic resin having low compatibility with the syntheticresin used in the outer layer.

The preform in the above configuration can be biaxially stretched andblow molded into a bottle consisting of the outer layer of a syntheticresin, which forms the outer shell of a definite shape, and the innerlayer of a synthetic resin, which forms the inner bag, with both layersbeing laminated in a separable manner. Such a bottle can be used as adelaminating bottle.

In another exemplary embodiment of the invention, the means of carryingout the invention comprises a bottom adhesive layer to adhere and fixthe outer layer and the inner layer together over the entire length ofthe pinch-off portion, which is formed when the portion of parison Pcorresponding to the bottom shell portion is forced to flatten by thepinch-off section of the split blow mold.

In the above-described configuration, the outer layer and the innerlayer are adhered firmly with each other by the bottom adhesive layerover the entire length of the pinch-off portion. Thus, the pinch-offportion can be prevented from being peeled and damaged especially by thestretch pin during the longitudinal stretching when the preform isbiaxially stretched and blow molded into a bottle. The molded bottle hasits outer and inner layers adhered firmly by the bottom adhesive layerover the entire length of the bottom seal. This bottom structure makessure of preventing the decrease in the mechanical strength of the bottomseal when such a decrease may be derived from the separable layers ofincompatible synthetic resin materials.

In still another exemplary embodiment of the invention, the means ofcarrying out the invention comprises the laminated wall structureconsisting of the outer layer, the inner layer, and at least a verticalslip-like adhesive layer to adhere and fix the outer and inner layerswith each other over the entire height of these layers.

When the preform is biaxially stretched and blow molded, the verticalslip-like adhesive layer adheres the outer layer with the inner layerover the entire height. The resultant adhered zone serves to prevent theinner layer from being distorted and deformed in the vertical directionand thereby to prevent the content flow passage from being blocked up inthe delaminating bottle.

The placement and the number of the vertical slip-like adhesive layercan be selected, depending on the purpose and necessity. For example, ifoutside air is sucked up through the bottom into the space between theouter layer and the inner layer, preferably the adhesive layer can belocated roughly on the parting line.

Usually, the delaminating bottles are molded by the direct blow methodbecause of its laminated structure. On the contrary, the blow moldedpreform in certain above-described exemplary configurations of theinvention can be biaxially stretched to obtain the bottle having higherstrength.

In another exemplary embodiment of the invention, the means of carryingout the invention comprises:

-   -   employing a blow-molded preform so that the preform is molded        into a bottle by a biaxially stretching and blow molding means;    -   providing the preform with a mouth portion;    -   providing the preform with a cylindrical barrel portion from        which the barrel is molded;    -   providing the preform with a bulging shoulder portion from which        the shoulder is molded, disposing this portion between the mouth        portion and the barrel portion, and allowing the bulging        shoulder portion to have the diameter that widens slightly in        the downward direction;    -   providing the preform with a bottom shell portion from which the        bottom is molded, and forming the bottom shell portion into an        almost spherical shape; and    -   providing the preform with an inner overhang wall portion an        inner overhang wall portion in any position starting from the        opposite side of the neck ring, which is disposed        circumferentially around the lower part of the mouth portion,        and ending at the upper portion of the bulging shoulder portion,        with said inner wall portion having a diameter that widens in        the downward direction.

Another exemplary means of carrying out the invention comprises:

-   -   employing a blow-molded preform so that the preform is molded        into a bottle by a biaxially stretching and blow molding means;    -   providing the preform with a mouth portion;    -   providing the preform with a cylindrical barrel portion from        which the barrel is molded;    -   providing the preform with a bulging shoulder portion from which        the shoulder is molded, disposing this portion between the mouth        portion and the barrel portion, and allowing the bulging        shoulder portion to have the diameter that widens slightly in        the downward direction;    -   providing the preform with a bottom shell portion from which the        bottom is molded, and forming the bottom shell portion into an        almost spherical shape; and    -   providing the preform with a radially widened connecting portion        connecting the lower part of the cylindrical barrel portion to        the bottom shell portion, with the connecting portion having a        larger diameter than the barrel portion.

In still another exemplary embodiment of the invention, the means ofcarrying out the invention comprises an inner overhang wall portion aninner overhang wall portion disposed in any position starting from theopposite side of the neck ring, which is disposed circumferentiallyaround the lower part of the mouth portion, and ending at the upperportion of the bulging shoulder portion, with the inner wall portionhaving a diameter that widens in the downward direction.

In yet another exemplary embodiment of the invention, the means ofcarrying out the invention comprises the reinforcing rib that isdisposed under the opposite side of the pinch-off portion in the bottomshell portion.

In certain of the above-described exemplary configurations, thick areasare prevented from occurring in the pinch-off portion and/or in theinner overhang portion in any position starting from the opposite sideof the neck ring and ending at the upper portion of the bulging shoulderportion even if the preform is of the single-layer wall structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram showing a mode of molding the preformof this invention into a bottle, with the right half being illustratedin longitudinal section.

FIG. 2 is a front view, with partial insection, of the entire preformaccording to the first shape embodiment of this invention, with animportant segment being illustrated in longitudinal section.

FIG. 3 is a front view of the entire preform according to the secondshape embodiment of this invention, with the right half beingillustrated in longitudinal section.

FIG. 4 is a front view of the entire preform according to the thirdshape embodiment of this invention, with the right half and thepartially enlarged pinch-off portion being illustrated in longitudinalsection.

FIG. 5 is an explanatory longitudinal section showing an example ofparison to be molded into the preform of this invention.

FIG. 6 is an explanatory diagram showing the preform according to thefourth shape embodiment of this invention and the bottle to be moldedtherefrom, with the right half being illustrated in longitudinalsection.

FIG. 7 is a partially enlarged front view of the entire preform of thisinvention, with the right half being illustrated in longitudinalsection.

FIG. 8 is a partially enlarged front view of the entire preform of thelaminated wall structure according to the eighth embodiment of thelaminated wall structure of the invention, with the right half beingillustrated in longitudinal section.

FIG. 9 is a plane cross-sectional view of the preform of this inventioncut from line A-A in FIG. 8.

FIG. 10 is a partially enlarged plane view of the preform bottom in thelaminated structure according to this invention.

FIG. 11 is an explanatory diagram showing the process for blow moldingthe parison into the preform according to the eighth embodiment of thelaminated wall structure of this invention.

PREFERRED EMBODIMENTS OF THE INVENTION

This invention is further described as to its preferred embodiments,while referring to the drawings. FIG. 1 is an explanatory diagramshowing a mode of molding the preform of this invention into a bottle,with the right half being illustrated in longitudinal section. Thepreform 1′ is stretched vertically and laterally into the bottle 1.

FIG. 2 is a front view, with partial insection, of the entire preform 1′according to the first shape embodiment of this invention in which thecylindrical, extrusion-molded parison P has been blow molded into thecylindrical preform of this invention having a closed end. Helicalridges are disposed on the outer circumference of the short cylindricalmouth portion, and the neck ring 3 is also disposed around the lowerpart of the mouth portion. Downward from the mouth portion 2 there isthe bulging shoulder portion 4′ (the portion to be molded into theshoulder 4 of the bottle 1) having a diameter that widens slightly inthe downward direction. Downward from this bulging shoulder portion 4′there is the cylindrical barrel portion 5′ (the portion to be moldedinto the barrel 5 of the bottle 1). Under the barrel portion 5′ there isthe bottom shell portion 7′ (the portion to be molded into the bottom 7of the bottle 1), which has a shape of almost spherical shell. Inaddition, the inner overhang wall portion 3′ is disposed on the oppositeside of the neck ring 3, and has a diameter that widens in the downwarddirection.

This inner overhang wall portion 3′ is disposed on the innercircumference on the opposite side of the neck ring 3, i.e., on theborder between the mouth portion 2 and the bulging shoulder portion 4′to be molded into the shoulder 4 of the bottle 1. The diameter of thisportion 3′ widens in the downward direction. Prior to the blow moldingof parison P into the preform 1′, a core guide 11 equipped with an airblow nozzle is thrust into the upper end of the parison P to form themouth portion 2 (See FIG. 5). At that time, a thick area tends to beformed in the lower part of the inner wall of the mouth portion 2because of the core guide 11 that has been thrust. This thick area isabsorbed in the inner overhang wall portion 3′ when the parison is blownmolded into the preform. Thus, the thick area is actually never formedin the lower part of the inner overhang wall under the mouth portion 2.

FIG. 3 shows the preform 1′ according to the second shape embodiment ofthis invention. It is a front view of the entire preform with the righthalf being illustrated in longitudinal section. The short, cylindricalmouth portion 2 is provided with helical ridges on the outercircumference and with the neck ring 3 at the lower part of the outercircumference. The bulging shoulder portion 4′ is disposed under themouth portion 2, and has a diameter that widens slightly in the downwarddirection. The cylindrical barrel portion 5′ is disposed between theshoulder portion 4′ and the bottom shell portion 7′ of an almostspherical shell shape. The radially widened connecting portion 6′ isdisposed under the barrel portion 5′ and is by itself the upper portionof this bottom bulb portion 7′, with this radially widened connectingportion having a larger diameter than that of the barrel portion 5′.

This radially widened connecting portion 6′ slightly bulges from underthe barrel portion 5′ at a position close to the bottom shell portion7′, where the pinch-off portion 8′ is disposed right at the bottomcenter. When the parison is blow molded into the preform, the radiallywidened connecting portion 6′ is stretched and deformed along with thebottom shell portion 7′ to the last moment of the molding operation. Asa result, the thick pinch-off portion 8′ is also stretched to a largeextent, and no thick area is formed in the bottom.

FIG. 4 shows the preform 1′ according to the third shape embodiment ofthis invention. It is a front view of the entire preform with the righthalf being illustrated in longitudinal section. It also shows apartially enlarged, longitudinal section of the pinch-off portion 8′.The preform has the inner overhang wall portion 3′ and the radiallywidened connecting portion 6′. In addition, a ridge-like reinforcing rib9′ is disposed right under the bottom shell portion 7′ of this preform.

Because of the inner overhang wall portion 3′, no thick area is formedin the wall under the mouth portion 2. Likewise, because of radiallywidened connecting portion 6′, the pinch-off portion 8′ of the bottomshell portion 7′ does not get thick and thus does not show any wrongmovement during the blow molding operation. Furthermore, even if a sinkmark is formed due to the welding failure in the parison P, thereinforcing rib can make up for the decrease in the weld area caused bythis sink mark. When the preform is biaxially stretched and blow moldedinto a bottle, the reinforced pinch-off portion 8′ can be blow moldedwithout rupture.

FIG. 6 is an explanatory diagram showing the preform 1′ in the fourthshape embodiment of this invention and the bottle 1 that is biaxiallystretched and blow molded from this preform.

The bottle 1 has a shape in which the barrel and the bottom are largelycaved inward and upward, respectively. The bulging shoulder portion 4′,the cylindrical barrel portion 5′, and the bottom shell portion 7′ has ashape similar to the shoulder 4, the barrel 5, or the bottom 7 of abottle 1, but on a reduced scale. The preform 1′ also has such a shapethat it gives a small percent of stretch in the vertical direction whenit is biaxially stretched and blow molded.

The preform 1′ of such a shape is allowed to have low percent of stretchin the vertical direction when the preform is biaxially stretched andblow molded. Even after the preform has been stretched by means of thestretch pin, each portion of the stretched preform has a shape similarto the respective portion of the bottle 1 on a reduced scale. In thenext step of lateral stretch, the percent of stretch can be set at aconstant level for each portion. Thus, even a bottle of the largelycaved shape can be faithfully reproduced, and the bottle 1 has highstability, good moldability, and uniform wall thickness.

Because the preform 1′ has the inner overhang portion 3′, no thick areais formed in the inner wall under the mouth portion 2. The bottom shellportion 7′ and the lower part of the cylindrical barrel portion 5′ havebeen subjected to widened deformation and expanded deformation to givethe shapes of the bottom 7 and the barrel 5 of the bottle 1 on a reducedscale. Thus, the thick pinch-off portion 8′, too, is stretched and doesnot remain thick.

The preform in each embodiment has a laminated wall structure. Anexample is as shown in FIG. 7. However, since the preform 1′ is a blowmolded article, the preform of the laminated structure can be readilymolded with high precision.

The preform 1′ of the laminated wall structure in the first embodimentof the laminated wall structure comprises the combinations of PET andPEN layers. The first combination comprises the outer PET layer 1 a andthe inner PEN layer 1 c. The second combination comprises the outer PETlayer 1 a, the middle PEN layer 1 b, and the inner PET layer 1 c. Thethird combination comprises the outer PEN layer 1 a and the inner PETlayer 1 c. The fourth combination comprises the outer PEN layer 1 a, themiddle PET layer 1 b, and the inner PEN layer 1 c. Each combination canalso be provided with an adhesive layer or layers 1 d between theselayers.

In order for the preform to have good moldability and for the moldedbottles to have high mechanical properties, the PET in use shouldpreferably have an inherent viscosity value (hereinafter referred to asIV value) at 0.9 or more. Likewise, the PEN in use should preferablyhave an IV value of 0.5 or more. Although PET and PEN resins containinga copolymer component can be used, it is preferred to use a PET resinwith an IV value of 0.75 or more in the case of amorphous PET.

For all the configurations in the first embodiment of the laminated wallstructure, heat-resistant bottles can be obtained without crystallizingthe mouth portion. The heat set during stretching and blowing gives theheat-resisting property to the bottles, when the PEN layer occupies 50%or more of the entire thickness at the mouth and 50% or less at thebarrel. If a PEN resin containing a copolymer component is used, it isnecessary to design the thickness of the mouth portion in response tothe PEN component to be used. For example, in the case of a PEN resincontaining 51% PEN component, it is preferred that the PEN resin layeroccupies 90% or more of the entire thickness at the mouth.

PEN is used as the inner layer 1 c in the first and fourth combinationsof the first embodiment of the laminated wall structure. This gives thebottles high chemical-resisting property (high resistance to alkalis).The PEN layer can be 1-20% in its thickness. The PEN layer containing acopolymer can also be utilized.

All the configurations in the first embodiment of the laminated wallstructure of this invention allow the bottle to have a UV-cuttingfunction for the UV rays having a wavelength of 370 nm or below, whenthe thickness of the PEN layer is set at 1-20%.

The preform 1′ of the laminated wall structure in the second embodimentof the laminated wall structure comprises the combinations of the outerand inner PET layers 1 a and 1 c with the middle layer 1 b using a gasbarrier resin. The first combination comprises the middle layer 1 b ofan ethylene vinyl alcohol copolymer. The second combination comprisesthe middle layer 1 b of polyamide containing the xylylene radicals, andthe third combination comprises the middle layer 1 b ofpolyacrylonitrile, with the adhesive layer or layers 1 d being laidbetween these layers.

This second embodiment of the laminated wall structure allows the bottle1 to have barrier properties against oxygen and carbon dioxide, as thebarrier is insufficient in the case of a single PET layer. In addition,the bottle 1 with no interlaminar separation can be obtained withoutfail. In order that the content can be prevented effectively fromoxidation, it is preferred from an effectiveness point of view to use agas barrier resin having an oxygen transmission coefficient of 1cc·mm/m²·day·atm (20° C.50% RH) or less.

The preform 1′ of the laminated wall structure in the third embodimentof the laminated wall structure comprises the outer layer 1 a ofpolyethylene or polypropylene and the inner layer 1 c of an ethylenevinyl alcohol copolymer or PET, adhered with each other by the adhesivelayer 1 d. The bottle 1 in this embodiment prevents effectiveingredients of the content, such as limonene and vitamins, from beingabsorbed by the bottle 1.

The preform 1′ of the laminated wall structure in the fourth embodimentof the laminated wall structure comprises the outer layer 1 a ofpolyethylene or polypropylene, the middle layer 1 b using, as a gasbarrier resin, the polyamide having xylylene radicals, and the innerlayer 1 c of polyethylene or polypropylene, adhered with one another bythe adhesive layers 1 d. This configuration gives the bottle 1 a highoxygen barrier property.

The preform 1′ of the laminated wall structure in the fifth embodimentof the laminated wall structure comprises the outer layer 1 a of nylon-6and the inner layer 1 c of polyethylene or polypropylene, adhered witheach other by the adhesive layer 1 d. This embodiment gives the thinbottle 1 having a high piercing strength and high surface gloss.

The preform 1′ of the laminated wall structure in the sixth embodimentof the laminated wall structure comprises the outer and inner layers 1 aand 1 c made of a virgin PET resin and the middle layer 1 b made of aregenerated PET resin. This embodiment makes it easy to control thelayer thickness, and enables the regenerated resin materials to besafely utilized. When bottles are collected separately, they can bedealt with as the single-layer PET bottles.

The preform 1′ of the laminated wall structure in the seventh of thelaminated wall structure embodiment comprises the outer PET layer 1 acontaining an anti-static agent, the middle PET layer 1 b containing aUV-absorbing agent, and the inner layer 1 c of a virgin PET resinmaterial. The preform gives effective antistatic property, and there isno loss of the UV-absorbing agent caused by bleed-out because it isadded to the middle layer. The bottle can be filled with the contentsafely in spite of these additives used in the bottle.

FIGS. 8-11 show the preform of the laminated wall structure in the 8thembodiment of the laminated wall structure of the invention. The wallcomprises the outer layer 1 a of a synthetic resin material, such aspolyethylene, polypropylene, or polyethylene terephthalate, to be moldedas the outer shell that has a necessary shape-retaining ability; theinner layer 1 c of a synthetic resin material, such as nylon, ethylenevinyl alcohol copolymer, or polyethylene terephthalate, which is lesscompatible with the material of the outer layer 1 a and which is moldedinto a bag capable of deflective deformation; and the vertical slip-likeadhesive layer 13 and the bottom adhesive layer 14 of an adhesive resinhaving a full adhesive property for both of the outer and inner layers 1a and 1 c.

A pair of the vertical slip-like adhesive layers 13 is disposed at thepositions opposite to each other on the parting line 23 (See FIGS. 8 and9).

The bottom adhesive layer 14 has some spread from the pinch-off portion8′ to a part of the bottom shell portion 7′. The bottom adhesive layer14 adheres and fixes the outer and inner layers, 1 a and 1 c, to eachother at the pinch-off portion 8′, where the outer layer 1 a on one sideis integrated with the outer layer 1 a on the other side through thebottom adhesive layer 14 and the inner layer 1 c. (See FIGS. 8 and 10.)

Although the preform 1′ comprises the outer and inner layers, 1 a and 1c, of synthetic resins that are less compatible with, and peelable from,each other, the decrease in mechanical strength of the bottom seal atthe pinch-off portion 8′ can be prevented securely by the bottomadhesive layer 14 when this preform 1′ is biaxially stretched and blowmolded into the bottle 1. The inner layer 1 c is deformed inward due tothe deflection caused by the decrease in content as the content ispoured out. This deflective deformation is controlled in the verticaldirection by the pair of vertical slip-like adhesive layers 13, whichare disposed in axial symmetry to adhere and fix the outer and innerlayers, 1 a and 1 c, over the entire height of the bottle 1. Theseadhesive layers also prevent the content flow passage from beingblocked, thus enabling the content to be poured out of the delaminatedbottle 1 to the last drip.

The preform 1′ provided with the vertical slip-like adhesive layer 13and bottom adhesive layer 14 can be prepared by the process describedbelow. (See FIG. 11) The multi-layer parison P is molded byco-extruding, from the dies 22 for multi-layer parison use, themulti-layers comprising the cylindrical outer layer 1 a, the cylindricalinner layer 1 c located inside the outer layer 1 a, a pair of thevertical slip-like adhesive layers disposed in axial symmetry on theparting line 23, and the cylindrical ring-like adhesive layer 16 that isdisposed between the outer layer 1 a and the inner layer 1 aintermittently at a predetermined interval.

In contrast to the outer layer 1 a, the inner layer 1 c, and a pair ofthe vertical slip-like adhesive layers, all of which are co-extrudedcontinuously, the ring-like adhesive layer 16 is co-extruded, notcontinuously but intermittently, by the controlled pressurization anddepressurization of the accumulator with which the resin feed section isequipped for the ring-like adhesive layer.

The pinch-off section of the split blow mold 10 pinches off themulti-layer parison P thus molded, laterally in the area where thering-like adhesive layer 16 has been formed. When the cut parison isblow molded, this ring-like adhesive layer 16 develops into the bottomadhesive layer 14, such as described in the preform 1′ of the laminatedwall structure in the eighth embodiment of this invention.

The bottle 1 obtained by the biaxially stretching and blow molding meanshas a higher strength than the strength of the bottle 1 made by thedirect blow because the former bottle is not only blown but alsostretched.

The percent of stretch in the stretching and blow molding operation canbe properly selected, depending on purpose, necessity, and theco-stretchability of each resin with which the laminated structure isorganized. However, the percent of stretch in the longitudinal directioncan be set at a low level so as to prevent the bottom from cracking dueto the vertical stretching.

This invention in the above-described configurations has the followingeffects.

No thick area is formed in the portion to be molded into shoulder and/orin the portion to be molded into the bottom of the bottle. As a result,the entire bottle can be molded with high precision of wall thickness togive the bottle having good appearance and no defective distortion.

The preform has been blow molded so that the cylindrical barrel portionis stretched and deformed, and the bottom shell portion has widened indiameter. With this configuration, the preform of this invention showshigh molding stability when it is biaxially stretched and blow moldedinto the bottle. Since the stretch is given to an extent enough to moldthe bottom, the bottom in a stable sitting position can be moldedwithout fail.

The bottle with laminated wall can be produced easily and securely, thusenabling the bottle to have desired physical properties and to makeeffective use of the material characteristics. Since the preform is anextrusion blow-molded article, it can be more readily molded in thelaminated structure than when the preform is produced by the injectionmolding.

Because the bottom shell portion has a roughly spherical shape invarious exemplary embodiments of the invention, it is possible to obtainthe preform that have been isotropically widened and deformed, merely byusing the mold of a simple shape. Especially in the bottle having abottom of a roughly isotropic cross section, the bottom of the preformis stretched almost uniformly in the circumferential direction.Therefore, there is no case where this distortion caused by the moldingmay deteriorate the appearance and shape of the bottle or where thebottom loses its stable sitting function.

In other exemplary embodiments of the invention, the preform comprisesthe bottom shell portion of a roughly spherical shape and a radiallywidened connecting portion of an arced shape, and this connectingportion has a larger diameter than the barrel portion so that thisportion makes an arc. With this configuration, the parison can be blowmolded in a mold of a simple shape to form the isotropically widenedbottom shell portion and the connecting portion. Especially in thebottle having the bottom of a roughly isotropic cross section, thebottom and the connecting portion of the preform are stretched almostuniformly in the circumferential direction. Therefore, there is no casewhere this distortion caused by the molding may deteriorate the bottleappearance and shape or where the bottom loses its stable sittingfunction.

In still other exemplary embodiments of the invention, the preform isgiven partly or entirely a bottle-like shape on a reduced scale. Such ashape gives the preform more uniform percent of stretch than usual, whenthe preform is biaxially stretched and blow molded into a bottle. Evenif the bottle has a complicated shape, such as being largelynon-isotropic or having a shape with various ups and downs, there can beobtained a less deformed bottle of uniform thickness with high stabilityand good moldability.

When a sink mark appears in the pinch-off portion because ofinsufficient weld strength caused by a welding failure, the preform invarious exemplary embodiments of the invention makes up for thisdefective portion fully and reliably. Since it is possible to enhancefully the weld strength at the pinch-off portion and the effect ofpreventing interlaminar separation, the preform can be biaxiallystretched and blow molded into the bottle safely and smoothly.

In other exemplary embodiments of the invention, the PET resin layer iscombined with the PEN resin layer. This combination serves to enhanceeffectively the properties that seem to be deficient in the PET resin,such as thermal resistance, resistance to chemicals, and the UV-cuttingproperty.

In other exemplary embodiments of the invention, there is obtained abottle having enhanced barrier properties against oxygen and carbondioxide, by using the middle layer of a gas barrier resin, as thesebarrier properties are deficient when a single PET layer is used.

In still other exemplary embodiments of the invention, the ethylenevinyl alcohol copolymer is used for the inner layer. The bottle 1 inthis embodiment prevents effective ingredients of the content, such aslimonene and vitamins, from being absorbed by the bottle 1.

In various other exemplary embodiments of the invention, the middlelayer of a gas barrier resin makes it possible to obtain the bottle of apolyolefin resin having a high barrier property against oxygen.

In other exemplary embodiments of the invention, the preform comprisesthe outer layer of a nylon resin. This embodiment gives the bottlehaving a high piercing strength and high surface gloss.

In other exemplary embodiments of the invention, the preform has thelaminated wall structure consisting of the outer and inner layers of avirgin resin material and the middle layer of a regenerated resinmaterial. The regenerated resin can be utilized safely in thisstructure.

In other exemplary embodiments of the invention, an anti-static additiveis added to the outer layer alone. Thus, with a small amount ofadditive, it is possible to prevent the bottle from beingelectro-statically charged over the outer surface where electrostaticcharge is a problem.

In still other exemplary embodiments of the invention, the UV-absorbingagent can be added to the most effective layer in response to the layerconfiguration and the application of the bottle.

In various other exemplary embodiments of the invention, the laminatedwall structure consists of the outer layer of a synthetic resin and theinner layer of another synthetic resin having low compatibility with thesynthetic resin used in the outer layer. In this configuration, it ispossible to obtain a bottle consisting of the outer layer of a syntheticresin, which forms the outer shell of a definite shape, and the innerlayer of a synthetic resin, which forms the inner bag, with both layersbeing laminated in a separable manner. Such a bottle can be used as adelaminating bottle.

In other exemplary embodiments of the invention, the laminated wallstructure also comprises the bottom adhesive layer that adheres firmlythe outer layer and the inner layer with each other over the entirelength of the pinch-off portion. In this configuration, the pinch-offportion can be prevented from being peeled and damaged especially duringthe longitudinal stretching. The bottom adhesive layer also makes surethat the delaminating bottle is prevented from the decrease in themechanical strength of the bottom seal.

In other exemplary embodiments of the invention, the laminated wallstructure also comprises the vertical slip-like adhesive layer or layersthat adhere the outer layer with the inner layer over the entire height.The resultant adhered zone or zones serve to prevent the inner layerfrom being deflected and deformed in the vertical direction and therebyto prevent the content flow passage from being blocked up in thedelaminating bottle.

In still other exemplary embodiments of the invention, even the preformof the single-layer wall structure has no thick area in the pinch-offportion and/or in the inner overhang portion in any position startingfrom the opposite side of the neck ring and ending at the upper portionof the bulging shoulder portion. It is also possible for thesingle-layer preform to have the fully enhanced weld strength for thepinch-off portion.

1. An extrusion blow-molded synthetic resin preform for molding a bottleby a biaxially stretching and blow molding means, said extrusion preformcomprising: a mouth portion having a neck ring; a cylindrical barrelportion from which a barrel is molded; a bulging shoulder portion to bemolded into a shoulder, said bulging shoulder portion existing betweenthe neck ring and the cylindrical barrel portion and having a diameterthat widens in the downward direction; a bottom shell portionblow-molded to have a widened and a desired shape; an inner overhangwall portion located in any position on an interior of the extrusionpreform starting from the opposite side of the neck ring, which isdisposed circumferentially around a lower part of the mouth portion andending at an upper portion of the bulging shoulder portion, with saidinner overhang wall portion having a diameter that continuously widensin the downward direction, wherein said extrusion preform has a wall ofa plurality of laminated layers.
 2. The extrusion blow-molded syntheticresin preform according to claim 1, wherein the bottom shell portion,from which a bottom is molded, has an almost spherical shape.
 3. Theextrusion blow-molded synthetic resin preform according to claim 1, formolding a bottle, wherein at least one of the bulging shoulder portion,the cylindrical barrel portion, and the bottom shell portion has areduced shape similar to a shoulder, a barrel, or a bottom of a bottle.4. The extrusion blow-molded synthetic resin preform according to claim2, wherein a reinforcing rib is projected from under a downside of apinch-off portion in the bottom shell portion.
 5. The extrusionblow-molded synthetic resin preform according to any one of claims 1-4,wherein the preform has the laminated wall structure consisting of atleast a polyethylene terephthalate resin layer and a polyethylenenaphthalate resin layer.
 6. The extrusion blow-molded synthetic resinpreform according to any one of claims 1-4, wherein the preform has alaminated wall structure consisting of at least outer and inner layersof polyethylene terephthalate and a middle layer of a gas barrier resin.7. The extrusion blow-molded synthetic resin preform according to anyone of claims 1-4, wherein the preform has a laminated wall structurecomprising at least an outer layer of polyethylene or polypropylene andan inner layer of an ethylene vinyl alcohol copolymer or a polyethyleneterephthalate resin.
 8. The extrusion blow-molded synthetic resinpreform according to any one of claims 1-4, wherein the preform has alaminated wall structure consisting of at least an outer layer ofpolyethylene or polypropylene, a middle layer of a gas barrier resin,and an inner layer of polyethylene or polypropylene.
 9. The extrusionblow-molded synthetic resin preform according to any one of claims 1-4,wherein the preform has the laminated wall structure consisting of atleast the outer layer of nylon and the inner layer of polypropylene orpolyethylene.
 10. The extrusion blow-molded synthetic resin preformaccording to any one of claims 1-4, wherein the preform has a laminatedwall structure consisting of at least outer and inner layers of a virginresin material and a middle layer of a regenerated resin material. 11.The extrusion blow-molded synthetic resin preform according to any oneof claims 1-4, wherein an outer layer of the laminated wall contains anantistatic additive.
 12. The extrusion blow-molded synthetic resinpreform according to any one of claims 1-4, wherein an outer layer ofthe laminated wall contains a UV-absorbing agent.
 13. The extrusionblow-molded synthetic resin preform according to any one of claims 1-4,wherein the preform has a laminated wall structure consisting of atleast an outer layer of a synthetic resin and an inner layer of anothersynthetic resin having low compatibility with the synthetic resin usedin the outer layer.
 14. The extrusion blow-molded synthetic resinpreform according to claim 13, wherein the preform has a laminated wallstructure consisting of the outer and inner layers and a bottom adhesivelayer to adhere these layers over an entire length of a pinch-offportion, which is formed when a portion of a parison corresponding tothe bottom shell portion is forced to flatten by a pinch-off section ofa split blow mold.
 15. The extrusion blow-molded synthetic resin preformaccording to claim 13, wherein the preform has a laminated wallstructure consisting of an outer layer and an inner layer and alsocomprising at least an adhesive layer of a vertical slip to adhere theselayers over an entire height of the preform.
 16. An extrusionblow-molded synthetic resin preform for molding a bottle by a biaxiallystretching and blow molding means, said extrusion preform comprising: amouth portion having a neck ring; a cylindrical barrel portion fromwhich a barrel is molded; a bulging shoulder portion to be molded into ashoulder, said shoulder portion existing between the neck ring and thecylindrical barrel portion and having a diameter that widens in thedownward direction; a bottom shell portion of a roughly spherical shape,from which a bottom is molded; and an inner overhang wall portionlocated in any position on an interior of the extrusion preform startingfrom the opposite side of the neck ring, which is disposedcircumferentially around a lower part of the mouth portion, and endingat an upper portion of said bulging shoulder portion, with said innerwall portion having an inner diameter that continuously widens in thedownward direction.
 17. The synthetic resin preform according to claim16, wherein a reinforcing rib is projected from under a downside of apinch-off portion in the bottom shell portion.